Conventionally, a thermal transfer type printing device has been widely utilized in which an ink ribbon is heated by a thermal head and ink applied to the ink ribbon is transferred and printed on a printing medium. In the printing device, ink having the same shape as an image printed on the printing medium is printed from the ink ribbon and thus, after printing is performed, printed traces of ink having the same shape as the printed image are left on the ink ribbon. Therefore, when the printed traces are observed or, when the portion of the ink ribbon which is left without being printed is thermally transferred again, the image printed on the printing medium can be recognized easily.
In recent years, a card issuing system provided with a thermal transfer type printing device in which, when a card is conveyed through a card conveying passage, character information or the like is printed on a surface of a card by a thermal head, a hot stamp or the like has been increasingly installed in a store of a financial institution such as a bank. In the printing device in the card issuing system, there is a risk that an administrator for the device can easily obtain the image printed on the card from the printed traces of ink which are left in the used ink ribbon, or that a third person can easily obtain the image printed on the card from the printed traces of ink which are left in the discarded and used ink ribbon. That is an important issue to be solved in these days when protection of personal information is regarded as very important.
Conventionally, a thermal transfer type printing device has been proposed which is capable of solving the above-mentioned problem (see, for example, Patent Literature 1). The printing device described in Patent Literature 1 includes an erasing thermal head for heating an ink ribbon after ink has been transferred to a member to be transferred by a thermal head, and a transferred roller to which ink of the ink ribbon heated by the erasing thermal head is transferred. Therefore, in the printing device, printed traces of ink having a shape different from the image printed on the member to be transferred are left in the used ink ribbon. Accordingly, in the printing device, the personal information printed on the member to be transferred can be protected.